Analyzing And Designing Integrated Antennas in Wireless Systems
Wireless systems are now ubiquitous in sensing, communication, and computing applications. These range from high-end, high-cost, high-power RF MIMO systems to low-cost analog sensors with integrated low-cost antennas. Design, analysis, and verification of such systems are challenging on a variety of fronts.
These systems tend to be complex! Multiple radios may exist with interference between each of them, and with antennas playing multiple roles. These systems naturally function at high frequencies, implying that there are significant full-wave effects, multiple resonances, and strong environmental effects. Antenna patterns, near field behavior, and impedances and bandwidth are also strongly dependent on interactions with the antenna environment. In embedded systems and integrated antennas, close coupling with circuit boards and components can strongly impact these. Multiple file formats for 3d sections, and designs from manufacturing layouts, drawing layouts, and package and board layout tools all need to be integrated into a 3d model for electromagnetic analysis. The EM tool of choice has to handle these complexities, scale, and heteregenous system effects!Most commercial tools either have the scale without the accuracy or needed 3D ability, or can do 3D simulation of very simple structures. See the application snippet on integrated antennas that describes this further and shows how PhysWAVE can handle these challenges.
Predicting Chip-Package-Board Radiation EMI-EMC Early in the Design Cycle: Can Your EM Solver Do That ?
Consider the following scenario. Switching logic for large on-chip blocks leads to power transients. These transients find their way through solder bumps or bond wires through to the package, and through solder balls into the board. These cause not only IR drop, and voltage and ground bounce, but also cause radiation and electromagnetic interference. This radiation or EMI may couple back into the system, cause undesired interference to other system, cause unacceptable loss and noise, and may also cause the system to violate EMC rules such as those set by the FCC.
Consider a slightly diffferent scenario, associated with signal waveforms rather than switching power waveforms. Consider a differentially designed channel. Unfortunately, common modes are almost always excited due to some assymetry in channels, impedance mismatches, and complexity of geometry and environment in the chip, chip-package interface, package, package-PCB interface or within the board. This so-called “differential EMI” (i.e. arising in differentially excited and designed systems) can also create undesired crosstalk and radiated fields.
The demands on an EM solver that can be used in such a scenario are extremely challenging. 3D full-wave accuracy is key, because interface and edge-effects, especially for systems with multiple or ill-defined references, are important in EMI. Quasi-static or 2.5D solvers will not cut it in this application. At the same time, this solver needs to scale to the full chip-package-board level to allow RDL and GDS layers, full-packages, and board nets to be simulated. The speed of the solver is critical: if early design is to be enabled, several design choices need to be considered on-chip, at the package, and in the PCB including routing, decap placement, logic switching and turn-off, etc. Finally, such a solver needs to interface with on-chip noise modeling tools and SPICE, such that noise models from library characterization or worst-case switching noise can be directly integrated. These are significant challenges of accuracy, compatibility, scale, and speed, where no compromises can be made by making rudimentary assumptions on 3D full-wave EM wave behavior.
